1. Field of the Invention
The present invention relates to a gaseous fuel injection valve for supplying a natural gas such as CNG and LPG as a fuel to an internal combustion engine, and particularly to an improvement in a gaseous fuel injection valve, comprising: a valve housing; a metallic nozzle member which is fixedly mounted at one end of the valve housing and which has a flat valve seat and a nozzle bore passing through a central portion of the valve seat; a valve body which is slidably fitted in the valve housing and which is provided at one end face with a rubber seating member for opening and closing the nozzle bore in cooperation with the valve seat; a coil supported in the valve housing; a stationary core which is connected to the valve housing and disposed inside the coil to be opposed the other end face of the valve body; and a return spring mounted under compression between the stationary core and the valve body so as to urge the valve body toward the valve seat, the stationary core attracting the valve body to move the seating member away from the valve seat when the coil is excited.
2. Description of the Related Art
Such a gaseous fuel injection valve is already known as disclosed in Japanese Patent Application Laid-open No. 8-28360.
Conventionally, in a fuel tank of a fuel supply system for an internal combustion engine using a natural gas as a fuel, a gaseous fuel charged in a fuel tank contains a small amount of a lubricating oil to be applied to various devices for a gaseous fuel supply source. Therefore, a small amount of the oil is also incorporated in the fuel supplied from the fuel tank to an injection valve. In the conventional gaseous fuel injection valve, if the oil is adhered to a flat valve seat, the oil induces a sucker effect in a valve seat with respect to a seating member upon seating of the valve body on the valve seat, particularly in a cold season in which the viscosity of oil is increased. Therefore, when the coil is excited, the sucker effect may provide a resisting force against the movement of the seating member away from the valve seat, resulting in a reduction in valve-opening response of the valve body.